Command line interfaces can often be composed of different modules responsible
for distinct actions. This package allows each such module to influence the
overall command line interface. First and foremost each module can add its own
option group with a specific title, description and a set of module specific
options (see Horde_Argv_OptionGroup for further details). In addition
Cli_Modular allows a module to modify the global usage string and add basic
options valid for all modules.